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Development of cryogenic payload for KAGRA I. K. Yamamoto , R. Takahashi, T. Sekiguchi, Y. Sakakibara, C. Tokoku, M. Kamiizumi, U. Iwasaki, T. Uchiyama, S. Miyoki, M. Ohashi, T. Akutsu A , H. Ishizaki A , T. Suzuki B , N. Kimura B , S. Koike B , K. Tsubono C , Y. Aso C ,

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slide1

Development

of cryogenic payload

for KAGRA I

K. Yamamoto, R. Takahashi, T. Sekiguchi, Y. Sakakibara, C. Tokoku,

M. Kamiizumi, U. Iwasaki, T. Uchiyama, S. Miyoki, M. Ohashi, T. AkutsuA,

H. IshizakiA, T. SuzukiB, N. KimuraB, S. KoikeB, K. TsubonoC, Y. AsoC,

T. UshibaC, K. ShibataC, D. ChenD, N. OhmaeE, K. SomiyaF, R. DeSalvoG,

E. MajoranaH, W. JohnsonI, KAGRA collaboration

ICRR.UT, NAOJA, KEKB, Phys.S.UTC, Astro.S.UTD, E.UTE,S.TITF,

Sannio Univ.G, INFNH, Louisiana State Univ.I

2012 September 11

The meeting of Physical Society of Japan

@Kyoto Sangyo University, Kyoto, Kyoto

1

slide2

0. Abstract

Progress of development

and near future plans

of cryogenic payload

(and cryocooler unitand cryostat)

for KAGRA in the last half year

slide3

Contents

  • Introduction
  • Cryocooler unit
  • Cryostat
  • Cryogenic payload
  • Summary
slide4

1. Introduction

KAGRA :

2nd generation interferometric

gravitational wave detector in Japan

Key features of KAGRA project

Silent underground site (Kamioka) :

Small seismic motion

Cryogenic system : Reduction of thermal noise

and so on

slide5

1. Introduction

Schematic view of KAGRA interferometer

Four mirrors of arm cavity will be cooled.

3km

3km

Mozumi

Y-end

Sakonishi

X-end

Kamioka mine

(Underground site)

Atotsu

Center

Vibration isolation system, Cryocooler unit, Cryostat, Cryogenic payload

5

5

slide6

1. Introduction

Outline of cryostat and cryocoolers

14m in height

Cryostat

Vibration

Isolation

(Type-A)

4 Cryocooler units

Cryogenic payload

Cryostat

Mirror

slide7

1. Introduction

Cryogenic payload

Outline of cryostat

to SAS

Mirror

Cryostat

Stainless steel t20mm

Diameter 2.6m

Height ~3.6m

M ~ 10 ton

View ports

4 Low vibration

cryocooler unit

~3.6m

Main LASER beam

2.6m

Cryo-coolers

Pulse tube, 60Hz

0.9 W at 4K (2nd)

36 W at 50K (1st)

Remote

valve unit

slide8

1. Introduction

Outline of cryogenic payload

Outer shield

(80K)

Vacuum chamber

(300K)

Inner shield

(8K)

Sapphire fiber

Heat links

(pure Al)

Sapphire mirror

(About 20K)

Y. Sakakibara

Classical and Quantum Gravity

(accepted)

8

slide9

2. Cryocooler unit

  • Outline

Pulse tube

cryocooler

(Sumitomo

Heavy Industries)

Vibration reduction system

9

9

slide10

2. Cryocooler unit

2. Drawing by Jecc Torisha

Pulse tube

cryocooler

Heat conductor

Cryostat

10

10

slide11

2. Cryocooler unit

3. Cooling test : Cryocooler works well.

2nd head

6.9 K (2.5 W heat load)

1st head

49.3 K (25 W heat load)

Y. Sakakibara’s talk

slide12

2. Cryocooler unit

4. Vibration measurement

Vibration of this part

was measured.

Pulse tube

cryocooler

Heat conductor

Cryostat

12

slide13

2. Cryocooler unit

4. Vibration measurement

T. Kume also proceeds with vibration measurement.

Institute for Cosmic Ray Research,

the University of Tokyo

slide14

2. Cryocooler unit

4. Vibration measurement

Displacement sensor

slide15

2. Cryocooler unit

4. Vibration measurement

Improvement is necessary…

Measurement with cryostat is necessary.

slide16

3. Cryostat

1. Assembly

Main body (Φ2.6m, H3.6m)

at Toshiba Keihin Product Operations

slide17

3. Cryostat

1. Assembly

at Toshiba Keihin Product Operations

Vacuum

chamber

slide18

3. Cryostat

1. Assembly

at Toshiba Keihin Product Operations

Vacuum

chamber

slide19

3. Cryostat

1. Assembly

at Toshiba Keihin Product Operations

Shield

slide20

3. Cryostat

2. Experimental plans in Toshiba

In this autumn, there will be cooling test of shileds in Toshiba Keihin Product Operations.

At the same time, we have experimental plans in Toshiba.

(1) Heat load test

(2) Measurement of vibration of shield

(3) Measurment of initial cooling time

slide21

3. Cryostat

2. Experimental plans in Toshiba

(2) Measurement of vibration of shield

Vibration of shield could be problems.

Vibration via heat links, Scattered light

This measurement is

at cryogenic temperature and in vacuum.

Luca Naticchioni (Rome) and Dan Chenwill measure vertical and horizontal vibration of radiation shield of KAGRA in cooling test, respectively.

D. Chen’s talk

slide22

3. Cryostat

2. Experimental plans in Toshiba

(2) Measurement of vibration of shield

Luca Naticchioni’s

accelerometer

slide23

3. Cryostat

2. Experimental plans in Toshiba

(3) Measurment of initial cooling time

Initial cooling time for cryogenic payload

is about 2 months (if no tricks).

At beginningof initial cooling,

heat transfer is dominated by radiation.

Diamond Like Carbon (DLC) coating

(High emissivity, Large radiation)

on shields and payload (except for mirror)

Y. Sakakibara’s talk

slide24

3. Cryostat

2. Experimental plans in Toshiba

(3) Measurment of initial cooling time

Initial cooling time with DLC (shield and mass)

Almost half !

Y. Sakakibara’s talk

slide25

3. Cryostat

2. Experimental plans in Toshiba

(3) Measurment of initial cooling time

We must check the effect of radiation (and DLC coating) on the initial cooling timeexperimentally.

We suspend something withoutheat link inside shield and monitor the temperature of something in shiled during cooling test.

What is something ?

Sample 1 : Sapphire and metal hollow sphere

Sample 2 : Dummy payload (hollow masses)

slide26

3. Cryostat

2. Experimental plans in Toshiba

(3) Measurment of initial cooling time

Sample 1 : Sapphire and metal hollow sphere

(100 mm in diameter)

(100 mm in diameter)

Scaling law

(Y. Sakakibara’s small experiment: 30 mm in diameter)

His talk

Evaluation of emissivity

slide27

3. Cryostat

2. Experimental plans in Toshiba

(3) Measurment of initial cooling time

Sample 2 : Dummy payload (hollow masses)

Half size

Hollow masses

(~5 kg)

DLC coating

Sapphire bulk as dummy mirror

Preparation is in progress.

slide28

4. Cryogenic payload

  • Mechanical simulation
  • T. Sekiguchi is developing.
  • (1) Vibration via heat links (above 1 Hz)
  • (2) Thermal noise (above 10Hz)
  • (3) Control scheme
  • (Investigation started recently)
slide29

4. Cryogenic payload

  • Mechanical simulation
  • (1) Vibration via heat links
slide30

4. Cryogenic payload

  • Mechanical simulation
  • (1) Vibration via heat links

Several peaks exceed the target sensitivity, but the flour level is OK.

Investivation (for safty margin) is in progress.

slide31

4. Cryogenic payload

  • Mechanical simulation
  • (2) Thermal noise

Now, we can calculate

thermal noise.

Not only sapphire

mirror and fibers

but also the other parts

must be consider

carefully.

We must proceed

with investiation.

slide32

4. Cryogenic payload

2. Sapphire fibers with nail heads

slide33

4. Cryogenic payload

2. Sapphire fibers with nail heads

Test sample (T. Uchiyama, ICRR)

slide34

4. Cryogenic payload

2. Sapphire fibers with nail heads

Sapphire fibers to suspend sapphire mirrors

Sapphire fibers from MolTech GmbH (Germany)

Length = 350 mm diameter = 1.8 mm

Almost as needed in bKAGRA.

Need to check the quality and improvement (T. Ushiba, K. Shibata).

34

slide35

4. Cryogenic payload

2. Sapphire fibers with nail heads

Ettore Majorana (Rome)

asked IMPEX HighTech GmbH

(German company).

They can make similar fibers

(nail heads on the both ends).

Shoter fibers (about 100 mm in length) is coming soon.

35

slide36

4. Cryogenic payload

2. Sapphire fibers with nail heads

Thermal conducutivity measurement : T. Ushiba

Q-value measurement in this autumn:

K. Shibata and Y. Sakakibara

36

slide37

5. Summary

  • Tests for cryocooler unit
  • Cooling : OK
  • Vibration : Almost OK
  • (some improvement is necessary)
  • Cryostat
  • Assembly is in progress in Toshiba.
  • In this autumn,
  • there will be cooling test of shileds.
  • In this test, we will try these experiments
  • (1) Heat load test
  • (2) Measurement of vibration of shield
  • (3) Measurment of initial cooling time

37

slide38

5. Summary

  • Cryogenic payload
  • Simulation tool
  • Vibration via heat link
  • Thermal noise
  • Control scheme
  • Investigation using simulation tool is in progress.
  • Sapphire fibers with nail heads
  • Moltech and IMPEX
  • Measurement of thermal conductivity
  • and Q-values is in progress.

38

slide40

4. Challenges for cryogenic

1. Issues of cooling : Reduction of heat load

(Scattering on mirror)

Scattering on mirror : 10 ppm ?

Scatted power is 5 W in radiation shield !

Cryostat scheme

4 cryocoolers coolradiation shields.

Payload is connected to radiation shield

by heat links.

If larger scattered light attacks shield,

mirror temperature must be higher.

40

40

slide41

4. Challenges for cryogenic

1. Issues of cooling : Reduction of heat load

(Scattering on mirror)

Scattering on mirror : 10 ppm ?

Scatted power is 5 W in radiation shield !

New cryostat scheme

2 cryocoolers cool radiation shields.

Other 2 cryocoolers cool payload

via separated heat path.

Even if large scattered light attacks shield,

mirror temperature could be low.

41

41

slide42

Sapphire fiber

2. Measurement Thermal conductivity (T. Ushiba)

Heat bath

temperature

sensor

L

Q

temperature

sensor

heater

42

slide43

Sapphire fiber

2. Measurement Thermal conductivity (T. Ushiba)

Heat bath

heat bath

temperature

sensor

temperature

sensor

L

Q

temperature

sensor

heater

heater

43

slide44

Sapphire fiber

2. Measurement Thermal conductivity (T. Ushiba)

  • We measured the thermal conductivity of Photoran’s sapphire rod without nail head whose surface is polished (before we try measurement for Moltech and IMPEX fibers). The diameter of the rod is 1.8 mm.
  • Result
  • 700 W/m/K @ 12K
  • 1100 W/m/K @ 17.5 K
  • Compared with Tomaru’s previous measurement, our result is a bit small.

44

slide45

Sapphire fiber

2. Measurement Thermal conductivity (T. Ushiba)

  • Something to be considered as the reason why the value of this measurement is small
  • the purity of the sapphire rod
  • So, we now measure thermal conductivity near 30 K (the peak of sapphire thermal conductivity) and confirm the purity is well or not.
  • If the purity of sapphire rod is not enough well, the peak of the thermal conductivity is gentle.

45

slide46

Sapphire fiber

2. Measurement Q-value (K. Shibata)

  • In KAGRA, we use sapphire rods to suspend mirrors.
  • The mechanical-Q of its bending modes are high. But it may depends on the surface condition.e.g.) as grown or polished, what manufactured it.

Moltech Sapphire rod φ1.8mm

46

slide47

Sapphire fiber

2. Measurement Q-value (K. Shibata)

  • We need to measure the mechanical-Q around 14-20K in advance.
  • By vibrating the supported point, we excite the bending modes. The amplitude is measured by the shadow sensor, and from the decay time, we estimate the mechanical-Q.
  • This experiment is done in KEK and will be finished by the end of this summer.

In/GaAs LED

Sapphire rod bounded by sapphire blocks

Photo detector

Bending modes are excitedby PZT’s vibration.

47

slide48

4. Challenges for cryogenic

2. Issues of noise : Vibration via heat links

Calculation

by T. Sekiguchi

(Details are

in his talk

on Tuesday)

T. Sekiguchi’s Master thesis (English)

http://gwdoc.icrr.u-tokyo.ac.jp/cgi-bin/private/DocDB/ShowDocument?docid=770

48

slide49

Baffle

Baffle for large angle scattering in cryostat

Optimal shape : T. Akutsu

Preliminary result

Reflection

(1.5*10-8)

Transmission

Mirror side

With DLC coating

49

49

49

slide50

2. Issues

(1)How to assemble

Details of construction, clean room ….

(2)Strength

Tensile strength, development of clamp, …

(3)Control system

Actuators (what and where),

resonant mode (frequency and Q)

slide51

2. Issues

(4)Cooling

Temperature of mirror, initial cooling time,

heat resistance …

(5)Noise

Thermal noise, vibration via heat links …

slide52

4. Summary

Cryogenic payload : One of key features of LCGT project

Cryogenic part of seismic isolation system

Cryostat installation in ICRR (Kashiwa) ~2013.3

(Check of cryostat system)

Check of cryogenic payload in ICRR

Preparation is in progress.

(1)Thermal simulation

(2)Sapphire fiber-mirror connection

(3)Simulation of effect of external vibration (with heat link)

(4)Thermal noise

slide53

5. Future work

(1)How to assemble

Details of construction, clean room ….

(2)Control system

Actuators (what and where),

resonant mode (frequency and Q)